Various types of stereoscopic projection optical systems are well known in the art. Such stereoscopic projection optical systems typically include two projectors arranged in parallel so that images from a liquid crystal display (LCD) panel or a slide film are projected on a screen by each light source. As shown in FIG. 4, a conventional stereoscopic projection optical system includes spherical reflective mirrors 1 and 1′, lamps 2 and 2′, condenser members 3 and 3′, LCD panels 4 and 4′, and projection lenses 5 and 5′.
In the conventional stereoscopic projection optical system, the stereoscopic picture is obtained by making the polarizing directions of projected beams perpendicular to each other. This is achieved by using two projectors. The picture from the right projector is only visible to the right eye of a viewer, and the picture from the left projector is only visible to the left eye of a viewer.
In the conventional stereoscopic projection optical system, the lamps 2, 2′ are independently operated. When the beams from each of the lamps 2, 2′ pass through the LCD panels 4, 4′ respectively, the beams are respectively polarized in the direction of a polarizing axis of a polarizing plate attached to the light source side of the corresponding LCD panels 4, 4′. As a result, half of the beams condensed by each of the condenser members 3 and 3 is absorbed by the polarizing plate before passing through the corresponding LCD panels 4, 4′. The lost light is absorbed as heat by the polarizing plate. This necessitates a separate cooling device to increase the heat-dissipating efficiency at the polarizing plates of the LCD panels 4, 4′.
It is desired to provide a stereo projection optical system which can overcome the above-described deficiencies.